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I spent three years going to Clayton before I bought a property there. In fact I have imaged at high resolution from a number of locations to find the best one before I found Clayton. South Australia luckily has pretty good seeing in general. At the time I was doing a lot of planetary imaging and wanted a good site with excellent regular seeing. I have had the site tested with a DIMM a couple of times and seeing has been tested being as good as 0.7 arc seconds on a good night but more regularly at around 1.4 arc second. The drought years made the seeing very good. The FWHM I regularly get now is about 1.4-1.7" these days on both the wide and narrow field systems. Still very respectable but a bit of an anomaly for sea level conditions from what I have seen discussed. I put it down the moisture content of the atmosphere and the prevailing winds on site and the topography of the location and intervening area. When the moisture content is low the seeing can be exceptional. Remembering back to my ten years on the east coast there was always a higher moisture content and general conditions were more humid, the landscape often rises high and steeply above the sea level and these factors no doubt cause turbulence in the atmosphere.
On poor nights at Clayton when the moisture content in the upper atmosphere is very high the seeing can be up around 2" FWHM. Those nights are rare though. The jet stream also seems to regularly miss my location too which is a fortunate situation.
From what I have heard and seen those numbers you list are about right for the conditions.
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